Surgical stapling apparatus with locking mechanism

ABSTRACT

The present disclosure provides for a loading unit for use with and/or supportable on a distal end of a surgical stapling apparatus. The loading unit includes a housing portion including a distal end and a proximal end, a drive assembly slidably supported within the housing portion of the loading unit, and a locking mechanism supported on the housing portion of the loading unit. The locking mechanism has a first position wherein the locking mechanism engages the drive assembly and maintains the position of the drive assembly in a ready-to-load position relative to the housing portion of the loading unit. The locking mechanism is pivotable to a second position wherein the locking mechanism disengages the drive assembly and enables the drive assembly to move relative to the housing portion.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of and priority to U.S. Provisional Application Ser. No. 60/545,621, filed Feb. 17, 2004, the entire content of which being incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a surgical apparatus, e.g., a surgical stapling apparatus. More particularly, the present disclosure relates to an endoscopic surgical stapling apparatus that includes a locking mechanism for retaining the drive assembly of a loading unit, e.g., a single use loading unit (“SULU”) or disposable loading unit (“DLU”), at a substantially fixed axial position until the SULU or DLU has been loaded with or secured to a surgical stapling apparatus, to ensure proper or complete engagement of the SULU or DLU, especially its drive assembly, to the surgical stapling apparatus. For simplicity, hereinafter, SULU or DLU will be referred to as “DLU”, but it should be understood to include either or both a DLU or SULU.

2. Background of Related Art

Surgical devices wherein tissue is first grasped or clamped between opposing jaw structure and then joined by surgical fasteners are well known in the art. In some instruments a knife is provided to cut the tissue which has been joined by the fasteners. The fasteners are typically in the form of surgical staples but two part polymeric fasteners can also be utilized.

Instruments for this purpose can include two elongated jaw members which are respectively used to capture or clamp tissue. Typically, one of the jaw members carries a staple cartridge which houses a plurality of staples arranged in at least two lateral rows while the other jaw member has an anvil that defines a surface for forming the staple legs as the staples are driven from the staple cartridge. Generally, the stapling operation is effected by cam members that travel longitudinally through the staple cartridge, with the cam members acting upon staple pushers to sequentially eject the staples from the staple cartridge. A knife can travel between the staple rows to longitudinally cut and/or open the stapled tissue between the rows of staples. Such instruments are disclosed, for example, in U.S. Pat. No. 3,079,606 and U.S. Pat. No. 3,490,675.

A later stapler disclosed in U.S. Pat. No. 3,499,591 also applies a double row of staples on each side of the incision. This patent discloses a surgical stapler that has a disposable loading unit in which a cam member moves through an elongate guide path between two sets of staggered staple carrying grooves. Staple drive members are located within the grooves and are positioned in such a manner so as to be contacted by the longitudinally moving cam member to effect ejection of the staples from the staple cartridge of the disposable loading unit. Other examples of such staplers are disclosed in U.S. Pat. Nos. 4,429,695 and 5,065,929.

Each of the instruments described above is designed for use in conventional surgical procedures wherein surgeons have direct manual access to the operative site. However, in endoscopic or laparoscopic procedures, surgery is performed through a small incision or through a narrow cannula inserted through small entrance wounds in the skin. In order to address the specific needs of endoscopic and/or laparoscopic surgical procedures, endoscopic surgical stapling devices have been developed and are disclosed in, for example, U.S. Pat. No. 5,040,715 (Green, et al.); U.S. Pat. No. 5,307,976 (Olson, et al.); U.S. Pat. No. 5,312,023 (Green, et al.); U.S. Pat. No. 5,318,221 (Green, et al.); U.S. Pat. No. 5,326,013 (Green, et al.); U.S. Pat. No. 5,332,142 (Robinson, et al.); and U.S. Pat. No. 6,241,139 (Milliman et al.), the entire contents of each of which are incorporated herein by reference.

Tyco Healthcare Group, LP, the assignee of the present application, has manufactured and marketed endoscopic stapling instruments, such as the Multifire ENDO GIA™ 30 and Multifire ENDO GIA™ 60 instruments, for a number of years. These instruments include a surgical stapling apparatus and a DLU. Typically, the DLU is attached to the apparatus immediately prior to surgery. After use, the DLU can be removed from the apparatus and a new DLU can be fastened to the apparatus to perform additional stapling and/or cutting operations. These instruments have provided significant clinical benefits. Nonetheless, improvements to these instruments are still possible.

It would be desirable to provide an improved DLU for a surgical stapling apparatus and an improved surgical stapling apparatus having the DLU loaded thereon.

It would also be desirable to provide a locking member for a DLU to assure proper loading of the DLU to the shaft of a surgical stapling apparatus.

Accordingly, it is an object of this disclosure to provide an improved DLU which locks or retains its drive assembly in proper position to be loaded onto the shaft of a surgical stapling apparatus (hereinafter referred to as the or a “ready-to-load position”) until the DLU is loaded onto a surgical stapling apparatus to assure that when the DLU is loaded thereto, the drive assembly is properly engaged by, coupled to or connected to a drive member of the shaft, thereby helping to ensure proper operation of the DLU and the surgical stapling apparatus. For example, with the DLU loaded onto the surgical stapling apparatus, after firing of the surgical stapling apparatus, retraction of the control rod will unapproximate or open and/or unclamp the anvil and cartridge assemblies.

An object of the disclosure is to provide an improved DLU that includes a locking mechanism that retains the drive assembly in such a ready-to-load position until the DLU is loaded onto the surgical stapling apparatus.

Another object of the disclosure is to provide such a locking mechanism for a DLU.

Another object of the present disclosure is to provide a locking mechanism for a DLU and a DLU having a locking mechanism, such that firing of the surgical stapling apparatus is prevented unless and until the DLU is loaded onto the shaft of the surgical stapling apparatus.

Yet another object of the disclosure is to provide a DLU that, after firing, can be disconnected from the surgical stapling apparatus.

Yet another object of the disclosure is to provide a DLU that has only two conditions, one in which it is not loaded and its drive assembly is locked or retained in the ready-to-load position, and another in which the DLU is loaded onto the shaft of a surgical stapling apparatus and in which the drive assembly is unlocked and free to be actuated.

Still another object of the present disclosure is to provide the above objects in a roticulating, i.e., roticulable, DLU.

SUMMARY

In accordance with the present disclosure, a surgical apparatus, e.g., a surgical stapling apparatus, including a locking mechanism for ensuring proper engagement of a disposable loading unit to an end of the surgical apparatus is provided. According to one aspect of the present disclosure the surgical apparatus includes a housing, a handle supported by the housing, and a loading unit supportable on a distal end of the housing. The loading unit includes a housing portion including a distal end and a proximal end, a drive assembly slidably supported within the housing portion of the loading unit, and a locking mechanism supported on the housing portion of the loading unit. The locking mechanism has a first position in which the locking mechanism engages the drive assembly and maintains the position of the drive assembly in a ready-to-load position relative to the housing portion of the loading unit. The locking mechanism is movable, preferably pivotable in a plane substantially tangential to an outer surface of the housing portion, to a second position in which the locking mechanism disengages the drive assembly and enables the drive assembly to move relative to the housing portion.

Preferably, the locking mechanism includes a lever having a distal end pivotably connected to the housing portion and a free proximal end, and a tooth extending radially inward from the lever. Desirably, the tooth selectively engages an engagement surface, e.g., a notch, formed in, on or of the drive assembly such that when the locking mechanism is in the first position the tooth engages the engagement surface of the drive assembly, and when the locking mechanism is in the second position the tooth is disengaged from the engagement surface of the drive assembly.

It is envisioned that when the locking mechanism is urged from the first position to the second position, the lever is pivoted about the distal end thereof such that a longitudinal axis of the lever is angled with respect to a longitudinal axis of the housing portion. The locking mechanism is preferably urged from the first position to the second position by a projection extending radially inward of the elongate body. Desirably, the projection acts on a side surface of the lever as the loading unit is twisted into loaded engagement in the elongate body.

Preferably, when the locking mechanism is in the first position the lever is substantially axially aligned with a nub extending radially outward from the proximal end of the housing and when the locking mechanism is in the second position the lever is out of axial alignment with the nub of the proximal end of the housing.

The proximal end of the lever can include a nub extending preferably radially toward, the proximal end of the housing. The proximal end of the housing preferably includes a recess formed in the surface thereof for receipt of the lever nub of the lever when the lever is in the first position.

The locking mechanism can further include a biasing member operatively associated therewith, wherein the biasing member tends to maintain the lever in the first position.

Preferably, the surgical apparatus is a fastener applier or stapler, preferably a laparoscopic or endoscopic stapler.

This disclosure also is of a DLU, preferably a roticulator DLU for a surgical fastener applier or stapler.

The surgical apparatus may further include an elongate body extending from the housing.

It is further envisioned that the proximal end of the housing portion of the loading unit may define an insertion tip.

The present disclosure further provides for a loading unit for use with and/or supportable on a distal end of a surgical stapling apparatus. The loading unit includes a housing portion including a distal end and a proximal end, a drive assembly slidably supported within the housing portion of the loading unit, and a locking mechanism supported on the housing portion of the loading unit. The locking mechanism has a first position wherein the locking mechanism engages the drive assembly and maintains the position of the drive assembly in a ready-to-load position relative to the housing portion of the loading unit. The locking mechanism is pivotable, in a plane substantially tangential to an outer surface of the housing portion, to a second position wherein the locking mechanism disengages the drive assembly and enables the drive assembly to move relative to the housing portion.

Additional advantages will become apparent from the description which follows, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be further described with reference to the accompanying drawings, wherein like reference numerals refer to like parts in the several views, and wherein:

FIG. 1 is a top perspective view of a preferred embodiment of the presently disclosed surgical stapling apparatus;

FIG. 2 is a top view of the surgical stapling apparatus shown in FIG. 1;

FIG. 3 is a side view of the surgical stapling apparatus shown in FIGS. 1 and 2;

FIG. 4 is a top perspective view of the surgical stapling apparatus of FIGS. 1-3 with the DLU disengaged from the elongate body of the surgical stapling apparatus;

FIG. 5 is a bottom perspective view of a non-articulating DLU for use with the surgical stapling apparatus of FIGS. 1-4;

FIG. 6 is a bottom perspective view of the preferred articulating DLU of the surgical stapling apparatus of FIGS. 1-4;

FIG. 7 is a top perspective view of the DLU of FIG. 6;

FIG. 8 is a top perspective view of the DLU of FIGS. 6 and 7;

FIG. 9 is a top perspective view, with parts separated, of the proximal housing portion and mounting assembly of the DLU of FIGS. 6-8;

FIG. 10 is an enlarged top perspective view, with parts separated, of a proximal portion of the upper housing half of the DLU of FIGS. 6-9;

FIG. 11 is a top perspective view of the proximal housing portion and mounting assembly of the DLU of FIGS. 6-9 with the upper half of housing portion removed;

FIG. 12 is a top perspective view, with parts separated, of a portion of the axial drive assembly of the DLU of FIGS. 6-9;

FIG. 13 is a top perspective view of the portion of the axial drive assembly of FIG. 11 of the DLU of FIGS. 6-9;

FIG. 14 is an enlarged top perspective view of a lower housing half of the housing portion of the DLU of FIGS. 6-9;

FIG. 15 is an enlarged perspective view of the distal end of the elongated body of the stapling apparatus shown in FIGS. 1-4, shown with the control rod extending therethrough;

FIG. 15 a is an enlarged perspective view of the distal end of the elongate body of FIG. 15, shown without the control rod extending therethrough;

FIG. 16 is an enlarged perspective view of the proximal end of the DLU of FIGS. 6-9 illustrating a locking mechanism according to the present disclosure;

FIG. 17 is an enlarged top plan view with portions broken away illustrating a stage in the attachment of the DLU of FIGS. 6-9 to the elongate body of the surgical stapling apparatus shown in FIGS. 1-3;

FIG. 18 is an enlarged top plan view with portions broken away illustrating another stage in the attachment of the DLU of FIGS. 6-9 to the elongate body of the surgical stapling apparatus shown in FIGS. 1-3;

FIG. 19 is an enlarged top plan view with portions broken away illustrating yet another stage in the attachment of the DLU of FIGS. 6-9 to the elongate body of the surgical stapling apparatus shown in FIGS. 1-3;

FIG. 20 is a longitudinal cross-sectional view of the proximal end of the DLU of FIGS. 6-9 as taken along line 20-20 of FIG. 16;

FIG. 21 is an enlarged transverse cross-sectional view of the proximal end of the DLU of FIGS. 6-9 with the distal end of the elongate body on the proximal end of the DLU as would be taken along 21-21 of FIG. 16, illustrating the locking mechanism in the first position; and

FIG. 22 is an enlarged transverse cross-sectional view of the proximal end of the DLU of FIGS. 6-9 with the distal end of the elongate body on the proximal end of the DLU as would be taken along 21-21 of FIG. 16, illustrating the locking mechanism in the second position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the presently disclosed surgical apparatus, DLU and locking mechanism or member will now be described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views.

In the drawings and in the description that follows, the term “proximal”, as is traditional, will refer to the end of the stapling apparatus which is closest to the operator, while the term “distal” will refer to the end of the apparatus which is furthest from the operator.

FIGS. 1-4 show a surgical apparatus, e.g., surgical stapling apparatus, generally referred to as 10. In the interest of brevity, this disclosure will focus primarily on systems, methods and structures for loading, engaging, coupling or connecting a disposable loading unit (“DLU”) 16 to surgical stapling apparatus 10. A detailed discussion of the remaining components and method of use of surgical stapling apparatus 10, is disclosed in U.S. Pat. No. 6,241,139.

Surgical stapling apparatus 10 is an endoscopic apparatus and includes a handle assembly 12 and an elongated body 14 extending from handle assembly 12. A DLU 16 is releasably secured to the distal end of elongated body 14. While this disclosure relates to the use of a DLU with surgical stapling apparatus 10, it is understood and within the scope of the present disclosure that a single use loading unit (SULU) or other end effector and/or tool assembly can equally be used in cooperation with surgical stapling apparatus 10.

DLU 16 includes a tool assembly 17 having a cartridge assembly 18 housing a plurality of surgical staples (not shown) and an anvil assembly 20 movably secured in relation to cartridge assembly 18. As shown herein, DLU 16 is configured to apply six (6) linear rows of staples, each row in the DLU's measuring from about 30 mm to about 60 mm in length. DLUs for applying any number of rows of staples, having staple pockets arranged in various patterns and/or DLUs and end effectors having any other lengths, e.g., 45 mm, are also envisioned. Handle assembly 12 includes a stationary handle member 22, a movable handle member 24, and a barrel portion 26.

A rotatable member 28 preferably is mounted on the forward end of barrel portion 26 to facilitate rotation of elongated body 14 and attached DLU 16 with respect to handle assembly 12. An articulation lever 30 preferably is also mounted on the forward end of barrel portion 26 adjacent rotatable member 28 to facilitate articulation of tool assembly 17. Preferably, a pair of knobs 32 are movably positioned along barrel portion 26. Knobs 32 are advanced distally to approximate or close cartridge and/or anvil assembly 18, 20, and retracted proximally to unapproximate or open cartridge and/or anvil assembly 18, 20.

As seen in FIG. 4, DLU 16 is desirably selectively removably couplable to elongated body 14. DLU 16 includes a housing portion 200 having a proximal end adapted to releasably engage the distal end of elongated body 14. A mounting assembly 202 is pivotally secured at 203 to the distal end of housing portion 200, and is configured to receive the proximal end of tool assembly 17 such that pivotal movement of mounting assembly 202 about an axis at 203 perpendicular to the longitudinal axis of housing portion 200 effects articulation of tool assembly 17.

FIGS. 5-8 show various perspective views of DLU 16. Surgical stapling apparatus 10 is capable of receiving a non-articulating DLU 16 a, as seen in FIG. 5, or an articulating DLU 16, as seen in FIGS. 6-8. U.S. Pat. No. 6,241,139 includes a detailed discussion of articulating and non-articulating DLU.

With reference to FIGS. 9-14, DLU 16 includes a mounting assembly 235. Mounting assembly 235 includes an upper and a lower mounting portion 236, 238, respectively. A centrally located pivot member 284 extends from each of upper and lower mounting portions 236, 238 through respective openings 246 a formed in coupling members 246. Coupling members 246 each include an interlocking proximal portion 246 b configured to be received in grooves 290 formed in the distal end of upper and lower housing halves 250, 252 to retain mounting assembly 235 and upper and lower housing halves 250, 252 in a longitudinally fixed position in relation to each other.

Upper housing half 250 and lower housing half 252 are contained within an outer sleeve, shell or casing 251. The proximal end of upper housing half 250 includes an insertion tip 193 extending proximally therefrom. Insertion tip 193 includes engagement nubs 254, preferably a pair of diametrically opposed engagement nubs 254, extending radially outwardly therefrom, for releasably engaging the distal end of body 14. Nubs 254 form a bayonet-type coupling with the distal end of body 14. Housing halves 252 and 254 define a channel 400 for slidably receiving axial drive assembly 212 therein. An articulation link 256 is dimensioned to be slidably positioned within a slot 402 formed in upper and lower housing halves 250, 252. A pair of blow out plate assemblies 255 are positioned adjacent the distal end of housing portion 200 adjacent the distal end of axial drive assembly 212 to prevent outward buckling and bulging of drive assembly 212 during articulation and firing of surgical stapling apparatus 10. For a detailed discussion of the structure and operation of blow out plate assemblies 255, reference is made to International Application Serial No. PCT/US02/32031, filed on Oct. 4, 2002, entitled “Surgical Stapling Device”, the entire content of which is herein incorporated by reference.

Referring to FIG. 9, optionally, a locking member 288 may be supported on engagement section 270 of axial drive assembly 212. In operation, when axial drive assembly 212 is actuated, by applying a predetermined force to movable handle member 24 to advance axial drive assembly 212 distally, locking member 288 provides an audible and tactile indication that surgical stapling apparatus 10 has been actuated. For a detailed discussion of the structure and operation of locking member 288, reference is made to the aforementioned International Application Serial No. PCT/US02/32031. Locking member 288 may also prevent inadvertent partial actuation of DLU 16, such as during shipping, by locking axial drive assembly 212 at a fixed position within DLU 16 until a predetermined axial force has been applied to axial drive assembly 212.

With reference to FIGS. 9-12, axial drive assembly 212 includes an elongated drive beam 266 (FIGS. 11 and 12) including a distal working head 268 (FIGS. 11 and 12) and a proximal engagement section 270. Drive beam 266 may be constructed from a single sheet of material or, preferably, multiple stacked sheets, as shown in FIG. 11. Engagement section 270 includes a pair of resilient engagement fingers 270 a and 270 b which are dimensioned and configured to mountingly engage a pair of corresponding retention slots 272 a and 272 b formed in drive member 272 (FIGS. 11 and 13). Drive member 272 includes a proximal porthole 274 configured to receive distal end 276 of a drive member, e.g., drive rod or control rod 52 (FIGS. 15 and 20-22) when the proximal end of DLU 16 is being engaged with elongated body 14 of surgical stapling apparatus 10. Control rod 52 functions to impart axial movement of drive assembly 212 from handle assembly 12.

As seen in FIGS. 9, 10 and 16-22, DLU 16 further includes a locking mechanism 300, preferably, pivotably supported on upper housing half 250. Locking mechanism 300 is manipulatable from a first position, in which drive assembly 212 is maintained in a ready-to-load position, to a second position, in which drive assembly 212 is free to move. DLU 16 is considered to be loaded to elongate body 14 when locking mechanism 300 is in the second position, i.e., when drive assembly 212 is connected to control rod 52 of elongate body 14. Locking mechanism 300 includes a lever 302 including a distal end 304 pivotally connected to upper housing half 250 and a free proximal end 306 in operative association with an outer surface of insertion tip 193. Desirably, distal end 304 is pivotably connected to upper housing half 250, via a pin 308 or preferably a ball-type pivot member. Alternatively, other known pivot structures formed integrally with or separate from upper housing half 250 may be used. Lever 302 further includes a projection, here shown as a tooth 310, extending radially inwardly from the inner surface of lever 302, preferably at a location between distal end 304 and proximal end 306.

In use, as best seen in FIGS. 16-22, when locking mechanism 300 is in the first position (i.e., in a ready-to-load, locked, or coupled position) (FIGS. 16, 17, 18, 20 and 21), lever 302 is substantially axially aligned with a longitudinal axis of housing portion 200 such that tooth 310 passes through an aperture 250 a formed in upper housing half 250 and is engaged with an engagement surface, e.g., a notch, shoulder or recess 270 c formed in the edge of engagement section 270 of drive assembly 212 to thereby effectively lock and maintain drive assembly 212 in the ready-to-load position wherein drive assembly 212 is in a retracted or proximal-most position relative to upper housing half 250. When DLU 16 is being coupled to the distal end of body 14, locking mechanism 300 ensures that engagement section 270 of drive assembly 212 is in a position to and properly engages, coupled with or connects to distal end 276 of control rod 52 (see FIGS. 20-22) of surgical stapling apparatus 10. Distal end 276 of control rod 52 has one or more engagement surfaces, preferably, and here shown as, including a head 276 a and a smaller diameter annular recess 276 b just proximal of head 276 a and partially defined by head 276 a. Thereafter, less preferably concomitantly therewith, locking mechanism 300 is manipulated (here rotated) to the second position wherein drive assembly 212 is in an unlocked, operative position in which lever 302 is angled with respect to the longitudinal axis of housing portion 200 such that tooth 310 is released from and/or otherwise disengaged from engagement surface 270 c of engagement section 270 of drive assembly 212 to free drive assembly 212 to move relative to housing portion 212, here, upper and lower housing portion 250, 252 of DLU 16.

When locking mechanism 300 is in the second position, DLU is considered loaded onto ad/or into elongate body 14 of surgical stapling apparatus 10. Thus, drive assembly 212 is free to be actuated and reciprocated axially by drive rod 52 to perform its operative functions of approximating and closing anvil and cartridge assemblies 18, 20, driving knife 280 and firing staples, as well as of un-approximating, un-clamping, and retracting drive assembly 212. DLU 16 is considered to be loaded to elongate body 14 when locking mechanism 300 is in the second position, i.e., when drive assembly 212 is connected to control rod 52 of elongate body 14.

With continued reference to FIGS. 15-20, preferably lever 302 of locking mechanism 300 further includes a nub or detent 314 extending radially inward from an inner surface 302 a of distal end 306 of lever 302. In use, nub 314 selectively engages and disengages a recess or dimple 193 a formed in the outer surface of insertion tip 193. Preferably, dimple 193 a is substantially in axial alignment with nubs 254 extending radially outward from insertion tip 193. Nub 314 and dimple 193 a create a snap-fit type engagement wherein nub 314 and dimple 193 a cooperate with one another to prevent and/or otherwise inhibit locking mechanism 300 from inadvertently or prematurely pivoting from the first position to the second position and thereby disengaging drive assembly 212. Locking mechanism 300 thus can include nub 314 and dimple 193 a.

Preferably, insertion tip 193 includes a recessed area 193 b (FIGS. 10 and 16) formed therein such that locking mechanism 300 does not extend radially outward beyond the outer surface of upper housing half 250. Lever 302 is able to pivot an amount sufficient to allow tooth 310 to disengage engagement surface or shoulder 270 c of engagement section 270 of drive assembly 212 when locking mechanism 300 is in the second position. Locking mechanism 306 preferably includes a spring or other biasing means 312 in operative association with lever 302 and housing portion 200 mounted and/or positioned in such a manner so as to bias lever 302 to the first position. As seen in FIG. 16, spring 312 includes an arm 312 a in contact with a side surface 302 a of lever 302 thereby tending to maintain lever 302 in the first position. The twisting force applied with respect to DLU 16 and/or elongate body 14 of surgical stapling apparatus 10 is sufficient to overcome the bias of spring 312 to allow lever 302 to move to the second position.

With continued reference to FIGS. 15-20, a method of use and/or operation of locking mechanism 300, in securing DLU 16 to the distal end of elongate body 14, will be discussed. Initially, with locking mechanism 300 in the first position such that tooth 310 is in locking engagement with shoulder 270 c of engagement section 270, to ensure that drive assembly 212 is in the proper position (e.g., in the proximal-most position) for coupling with head 276 a of distal end 276 of control rod 52, insertion tip 193 of DLU 16 is introduced longitudinally into the distal end of elongate body 14, in the direction of arrow “A”, such that nubs 254 slide into channels 276 d, through and past projections 276 c (see FIGS. 15 and 15 a) extending radially inward from elongate body 14 of surgical stapling apparatus 10 near the distal end thereof.

When nubs 254 have reached slots 276 e, and when insertion tip 193 has been fully inserted into the distal end of elongate body 14, DLU 16 is rotated, in the direction of arrow “B” (see FIG. 21). At this point in the coupling, rotation of DLU 16 results in three separate actions, namely, nubs 254 enter slots 276 e, thus connecting DLU 16 to distal end 14 of stapling apparatus 10; projections 276 b of firing rod 52 engage sections 270 a and 270 b of drive assembly 212, thus connecting firing rod 52 and drive assembly 212; and side wall of channel 276 d urges lever 302 (such that side wall of channel 276 d abuts against and engages proximal end of lever 306, preferably against a side surface 302 b of lever 302) of locking mechanism 300 to pivot from the first position to the second position about pivot pin “P” to thereby disengage tooth 310 from shoulder 270 c of engagement section 270 and thereby free drive assembly 212 to allow movement of drive assembly 212 and permit operation or continued operation of surgical stapling apparatus 10.

As can be appreciated, if lever 302 has been inadvertently moved to the second position, prior to coupling of DLU 16 to elongate body 14, and drive assembly 212 has prematurely moved from its proximal-most or ready-to-load position, lever 302 can not move to the first position since tooth 310 is not aligned with drive assembly 212 and can not pass in front of shoulder 270 c. In such a situation, tooth 310 will abut against a portion of engagement section 270 to prevent lever 302 from returning to the first position. Thus, upon insertion of DLU 16 into elongate body 14, proximal end 306 of lever 302 will abut against and/or otherwise contact projection 276 c of elongate body 14 and thus prevent loading of DLU 16 to elongate body 14.

Accordingly, the attachment of a DLU having a drive assembly which is not in its proximal-most or ready-to-load position is prevented.

It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto. 

1. A surgical apparatus comprising: a body; a handle supported by the body; and a loading unit supportable on a distal end of the body, the loading unit including: a housing portion including a distal end and a proximal end; a drive assembly supported for axial movement within the housing portion of the loading unit, the drive assembly having a proximal-most position relative to the housing portion of the loading unit; and a locking mechanism supported on the housing portion of the loading unit, the locking mechanism having a first position wherein the locking mechanism engages the drive assembly and maintains the drive assembly in the proximal-most position, the locking mechanism being movable to a second position wherein the locking mechanism disengages the drive assembly and allows the drive assembly to move relative to the housing portion.
 2. The surgical apparatus of claim 1, wherein the locking mechanism includes: a lever having a first end pivotably connected to the housing portion and a second free end; and a projection extending radially inward from the lever, wherein the projection selectively engages an engagement surface formed on the drive assembly such that when the locking mechanism is in the first position the projection engages the engagement surface of the drive assembly and when the locking mechanism is in the second position the projection is disengaged from the engagement surface of the drive assembly.
 3. The surgical apparatus of claim 2, wherein the body comprises an elongate body and has a control rod disposed therein for axial movement, the control rod being operatively connected to the handle.
 4. The surgical apparatus of claim 3, wherein the drive assembly is in a position to connect to a distal end of the control rod when the drive assembly is in the proximal-most position.
 5. The surgical apparatus of claim 3, wherein when the locking mechanism is moved from the first position to the second position, the lever is pivoted about the distal end thereof such that a longitudinal axis of the lever is angled with respect to a longitudinal axis of the housing portion.
 6. The surgical apparatus of claim 5, wherein the elongate body has a channel for receiving a proximal end of the loading unit.
 7. The surgical apparatus of claim 6, wherein the locking mechanism is moved from the first position to the second position by a wall defined in the channel of the elongate body, the wall acting on a side surface of the lever as the loading unit is rotated into loaded engagement in the elongate body.
 8. The surgical apparatus of claim 2, wherein when the locking mechanism is in the first position the lever is substantially axially aligned with a nub extending radially outward from the proximal end of the housing portion and when the locking mechanism is in the second position the lever is out of axial alignment with the nub of the housing portion.
 9. The surgical apparatus of claim 2, wherein the proximal end of the lever includes a detent extending toward the proximal end of the housing portion, and wherein the proximal end of the housing portion includes a recess formed in the surface thereof for receipt of the detent of the lever when the lever is in the first position.
 10. The surgical apparatus of claim 9, wherein the locking mechanism further includes a biasing member operatively associated therewith, wherein the biasing member tends to maintain the lever in the first position.
 11. The surgical apparatus of claim 4, wherein the surgical apparatus is a stapler.
 12. A method of loading a loading unit for a surgical apparatus: providing a loading unit having a locking mechanism in a first position, the loading unit having a drive assembly supported for axial movement within a housing portion of the loading unit, the drive assembly being engaged by the locking mechanism when the locking mechanism is in the first position; providing an elongate body and a handle supported by the elongate body, the elongate body having a distal end configured to be assembled with a proximal end of the loading unit, the distal end of the elongate body being configured to move the locking mechanism; assembling the proximal end of the loading unit with the distal end of the elongate body so that the locking mechanism moves to a second position wherein the locking mechanism disengages the drive assembly.
 13. The method of claim 12, wherein the locking mechanism is moved to the second position upon rotation of the loading unit.
 14. The method of claim 13, wherein the elongate body has a channel for receiving the proximal end of the loading unit.
 15. The method of claim 14, wherein the channel defines a wall for moving the locking mechanism upon rotation of the loading unit.
 16. The method of claim 12, wherein the locking mechanism includes a lever with a projection that engages the drive assembly when the locking mechanism is in the first position.
 17. The method of claim 16, wherein the lever pivots to the second position so that the projection disengages the drive assembly.
 18. The method of claim 14, wherein the proximal end of the loading unit defines at least one nub, and wherein assembling the loading unit includes rotating the loading unit so that the at least one nub enters a slot defined in the channel of the loading unit. 